DC to DC power converters accept an input voltage and convert it to a variable or fixed output voltage. They are used, for example, in consumer, industrial, aerospace and telecommunications applications. Some types are used in the energy storage modules of sensitive or critical electronic equipment.
Energy storage modules are often used to provide a backup supply voltage. A DC to DC power converter is used in these modules to transfer power from a primary power source to a storage component. When the system's primary power input is lost, the stored energy is supplied by the energy storage module to prevent, for a time, a disruptive shut off.
One type of known unidirectional DC to DC converter is a buck converter. In a buck converter, the input voltage is always greater than the output voltage. In a second type of uni-directional DC to DC converter, called a boost converter, the input voltage is always less than the output voltage. In yet a third type of converter, the buck-boost converter, an output voltage either greater than or less than the input voltage can be obtained.
A drawback of uni-directional converters, as far as their use in energy storage modules is concerned, is that their electrical circuits are not capable of bi-directional operation. They can operate in a charging mode or a discharging mode, but they cannot be switched between the two modes. If it is desired to include both functionalities, two circuits, one for charging and one for discharging, are required. This increases the size, complexity and expense of the converter.
FIG. 1 depicts a known bi-directional DC to DC converter. The inductive component of this converter receives an input current from the V.sub.1 input even when the left-most switch is open. Such converters have a large inrush current at start up and are difficult to control. In addition, a large duty cycle variation in both the charging and discharging modes causes them to be inefficient.
FIG. 2 depicts a known bi-directional full bridge DC to DC converter used for high voltage applications. This converter, however, requires eight switch components. As a result, it is larger and more complex than is desired.
Consequently, there exists a need for a smaller, more efficient bi-directional DC to DC converter. Further, there exists a need for a user-definable, bi-directional DC to DC converter, having a faster response time, no inrush current problem, and suitable for uninterrupted power supply applications.